HIV-1 infection is initiated by attachment of the virus to the target cell surface via high affinity interactions of the envelope glycoprotein to the CD4 cell surface receptor. Viral entry occurs following interaction of the viral envelope protein with cellular surface proteins designated as co-receptors. This essential fusion reaction is mediated by two newly described co-receptor molecules, CCR5 and Fusin. The tropism for these different co-receptors resides in the envelope region of HIV. T-cell tropic viruses tend to use the Fusin transmembrane protein while macrophage tropic viruses primarily use the chemokine receptor, CCR5. Recently, it has been demonstrated that a 32 base pair deletion within the coding sequence of the CCR5 gene is present at a frequency of approximately 20% in Caucasian population. Homozygous deletions occur in about 1% of the Caucasian population. These individuals do not express any CCR5 at the cell surface. Individuals harboring the homozygous deletion are markedly resistant to HIV-1 infection, but otherwise have no known health defects. Individuals heterozygous for this allele, although not immune to HIV-1 infection, appear to have a prolonged course of progression to AIDS and HIV related complications. These observations have led to the hypothesis to be tested here that down regulation of CCR5 by a ribozyme could have a marked impact on both the prevention and management of HIV infection. The proposed studies will examine the HIV-1 protective effects of ribozymes targeted to CCR5 in combination with anti-HIV-1 ribozymes and in vitro evolved Rev binding element decoys (aptamers). Monocytic cell lines will be used to evaluate the anti-HIV-1 efficacy of the CCR5 ribozyme and multivalent ribozyme/aptamer combinations. Ultimately the target cells for this novel gene therapy treatment are CD34+ human hematopoietic progenitor cells. These genetically modified cells will be tested for their ability to undergo multilineage differentiation into HIV-1 resistant cell populations. It is intended that these studies will lead to improved gene therapy treatment for HIV-1 infection. This proposal is project 3 of an interactive set of proposals with Dr. Ramesh Akkina (Project 1-SCID-hu mouse model) and Dr. Alan Knutsen (Project 2-In vitro thymopoiesis).